Further observations on some blackflies (Diptera: Simuliidae) associated with mayflies (Ephemeroptera: Baetidae and Heptageniidae) in Cameroon

An account is given of the infestation rates, attachment sites, larval size distribution and dispersion of Simulium baetiphilum on nymphs of Baetidae. The mechanisms of choice shown by S. afronuri and S. lumbwanum infesting Afronurus spp. are discussed.     

Visual Evaluation and Recognition of Hosts by the Tick Parasitoid, Ixodiphagus hookeri (Hymenoptera: Encyrtidae)

The role of host size, movement, feeding status, color, and species in the visual host evaluation and recognition behavior of the tick parasitoid, Ixodiphagus hookeri Howard was investigated. Freshly emerged female parasitoids were subjected to a choice bioassay, where the test materials were placed in sealed vials and the vials placed in a Petri dish. When presented with A. variegatum live and mummified nymphs, females examined: larger nymphs significantly longer than smaller nymphs, fed nymphs significantly longer than unfed nymphs, dead and live nymphs for similar lengths of time, and grey live nymphs and yellow-brown and dark brown mummified nymphs for similar lengths of time. The total number of visits to vials containing these test materials were also not significantly different, except there were significantly more visits to yellow-brown mummies when compared to the number of visits to dark brown mummies. When presented with A. variegatum (host) and R. appendiculatus (nonhost) nymphs, the females examined A. variegatum nymphs significantly longer than R. appendiculatus nymphs. The total number of visits to vials containing A. variegatum nymphs were significantly more than the visits to the vials containing R. appendicualtus nymphs. Furthermore, females spent significantly more total examination time per visit on larger and fed A. variegatum nymphs when compared to smaller and unfed nymphs, respectively. Direct and indirect detection were significant when females were presented with fed versus unfed A. variegatum nymphs, grey nymphs versus yellow-brown mummies, and R. appendiculatus versus A. variegatum nymphs. Direct and indirect detection for the rest of the bioassays were not significantly different. Finally, The percentages of females contacting large fed A. variegatum nymphs first were significantly different from those of females contacting small unfed R. appendiculatus nymphs first. The firstcontact percentages for the rest of the bioassays were not significantly different.     

Two phoretic black-flies (Diptera: Simuliidae) and their associated mayfly host (Ephemeroptera: Heptageniidae) in Cameroon

Simulium afronuri and S.lumbwanum are recorded living in association with nymphs of Afronurus in the forest zone of West Cameroon. Observations on infestation rates, attachment sites, larval size distribution and dispersion are recorded. Evidence of niche separation between the two simuliid species is discussed.     

The evolution of Heterocloeon with the first larval description of Heterocloeon frivolus comb. n. (Ephemeroptera: Baetidae)

The larva of Heterocloeon frivolus (McDunnough) comb. n. is described for the first time. Larval morphology indicates that the species be removed from Baetis and placed in the monophyletic genus Heterocloeon and indicates a relatively ancestral position of the species among congeners of Heterocloeon. On the basis of considerable new data, a previous phylogeny is falsified in part and a new phylogeny of Heterocloeon is hypothesized. Heterocloeon petersi and berneri are considered to be advanced sibling species. It is also deduced that Heterocloeonshared a recent commonancestor with Pseudocloeon and certain derived Baetis.     

Blatticola monandros n.sp. (Nematoda: Thelastomatidae) from the blattellid cockroach Parellipsidion pachycercum

Abstract

Blatticola monandros n.sp. occurs in the hind gut of nymphs and adults of the endemic New Zealand cockroach Parellipsidion pachycercum. It is distinguished from all other species of Blatticola in morphology — both sexes are smaller, the oesophagus is proportionately longer, and the spicule is shorter. The size of the nematode increases with the size of the host.     

Prey‐mediated changes in the selectivity of the predator Macrolophus pygmaeus (Heteroptera: Miridae)

When foraging in communities with mixed prey, generalist predators may be confronted with prey species that differ in quality, size and mobility and interact with one another. To examine prey selection, predation by Macrolophus pygmaeus (Heteroptera: Miridae) was recorded by providing a diet of either one or two prey species of Myzus persicae (third‐instar nymphs), Aphis gossypii (fourth‐instar nymphs), Trialeurodes vaporariorum (third‐instar nymphs) and Ephestia kuehniella (eggs). In the experiments, prey mobility, prey quality and prey biomass were considered. The biomass consumed by the predator was dependent on the combination of prey species and the quantity of biomass offered. In choice experiments with diets mixed of two prey species at equal densities, the predation to A. gossypii was significantly reduced in the presence of E. kuehniella but the rate of consumption of M. persicae, T. vaporariorum and E.kuehniella was not significantly affected by the coexistence of any other species in the mixed prey diet. When equal amounts of biomass from two prey species were provided in combination, the total consumed biomass was significantly reduced in the mixed prey diets composed of E. kuehniella eggs and aphid nymphs. Thus, under the mixed‐prey situation, prey selection by predators may be affected by interactions among prey species differing in traits such as quality, mobility and size.     

Size-related shifts in the physical habitat of two mayfly species (Ephemeroptera)

1. The spatial niche shifts of the nymphs of two mayfly species (Rhithrogena semicolorata and Ecdyonurus sp, gr. venosus) in relation to their growth were investigated in two lowland springs of northern Italy where they are dominant species. 2. Ordination of the different size classes of the two species revealed a canonical trend related to season and bottom roughness. 3. Larger nymphs of both species colonized rougher substrata. Differences between species in the roughness of areas colonized by small nymphs, which were very numerous, may have been due to competition for space.     

The diet of two species of Isoperla (Plecoptera: Perlodidae) in relation to season,site, and sympatry

The seasonal change in gut contents of nymphs of Isoperla grammatica and I. difformis from six streams in southern Sweden was analysed. Both species had ingested a variety of benthic prey and vegetable matter, predominantly diatoms. Some seasonality was evident with high percentages of diatoms in spring in I. grammatica, and in autumn in I. difformis. The scope of food was larger in the latter species which contained about equal proportions of vegetable matter, chironomids, mayfly, stonefly, and black fly larvae. In I. grammatica plant matter and chironomids dominated strongly, comprising > 50% of the gut contents on an annual basis, > 90 % in spring. While small nymphs of I. difformis contained a low proportion of animal matter, only gradually increasing with size, the nymphs of I. grammatica were carnivorous from very early instars. Both species switched to a temporarily strong utilization of algae in spring. This differed among sites, and appeared to reflect differences in insolation and thus the availability of algae. There was a significant negative relationship between the mean densities of Isoperla nymphs and the proportion of animal material found in the guts of I. grammatica (R ² = 0.86). Considering the density of I. grammatica alone, the relationship was weaker (R ² = 0.56). A positive correlation between predator and prey size was observed. With chironomid prey the size range increased with predator size. With simuliid prey, however, prey size increased with predator size in such a way that it suggests selection rather than just an expanding prey size range. Correlations were stronger and regression coefficients significantly higher for I. grammatica than for I. difformis. We suggest that I. grammatica, which ingests a much wider size range of prey might choose prey of optimal sizes more readily than the more synchronously developing I. difformis. Although the life cycles of the two species are staggered, overlap in size distribution indicates that competition for food could be important in spring. However, observed differences in diet should facilitate coexistence. Gut content differences might in turn be accomplished through microhabitat segregation.     

Ant Defense of Euphyonarthex phyllostoma (Homoptera: Tettigometridae) during Trophobiotic Associations1

During a five‐year field study, we made observations and conducted experiments to demonstrate unequivocally that Euphyonarthex phyllostoma (Fulgoromorpha: Tettigometridae) is a myrmecophile. Isolated adults and colonies always were found in association with ants. Colonies were associated only with Camponotus brutus or C. acvapimensis (For‐micinae), whereas isolated adults were attended by ants belonging to several species of Formicinae, Dolichoderinae, and Myrmicinae. The size of the planthopper colonies reached higher levels when attended by C. brutus than by C. acvapimensis. Experiments using ant exclusion showed that both ant species protected egg masses against parasitic wasps, but egg masses were less parasitized on trees occupied by C. brutus than on those occupied by C. acvapimensis (P = 0.0052). The production of egg masses by female hoppers was recorded only when C. brutus, C. acvapimensis, or the myrmicine ant Myrmicaria opaciventris attended the hopper. In both former cases, the presence of ants influenced the aggregation of the nymphs as they dispersed when ants were excluded. The aggregation of the nymphs ensured chat they were properly attended. Parental care by the females was reduced to their presence above or close to the egg masses. In fact, specialized workers of the attending ant species protected the egg masses as well as nymphs.     

Prey preference and consumption capacity of Nephus arcuatus (Coleoptera: Coccinellidae): the influence of prey stage,prey size and feeding experience

This study examined the feeding habits of Nephus arcuatus Kapur (Coleoptera: Coccinellidae), an important predator of mealybugs in south-western Iran. The consumption capacity of male and female N. arcuatus adults was determined by their feeding on eggs, first-instar nymphs, and adult females of two destructive mealybugs, Nipaecoccus viridis (Newstead) and Planococcus citri Risso, over a 24-h period. N arcuatus consumed significantly more first-instar nymphs than eggs, and more eggs than female adults of both prey species. In addition, we also studied the developmental stage prey preference of adults reared on either N. viridis or P. citri and found that the prey preference of females did not change with the developmental stage of the mealybug. Meanwhile, the males reared on either N. viridis or P. citri showed a significant preference for the first-instar nymphs of P. citri over first-instar nymphs of N. viridis, while a preference for the eggs or adult females of these two mealybugs was not observed. This selection of first-instar nymphs by males was not tied to its previous feeding experience. Our findings suggest that prey stage, prey size and previous feeding experience had no effect on the prey selection of N. arcuatus, making it a good candidate for the biological control of mealybugs.     

Efficacy of multiple biocontrol agents against the sweet potato whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on tomato

Abstract: Biological control provides an environmentally harmonious and potentially stable management tactic to combat noxious pests such as Bemisia tabaci, notorious for its resistance to synthetic pesticides. Bioassays conducted under control chamber conditions integrating applications of the parasitoid Encarsia formosa, reared for 20 years on Trialeurodes vaporariorum, and the fungus Verticillium lecanii on the third‐fourth instar nymphs of B. tabaci on tomato, showed a comparable effect between the parasitoid‐fungus combined treatment and the fungus treatment alone (70.7% vs. 70.4%). Analysis of our results indicates antagonism between the two biocontrol agents related to the parasitoids’ ability to discriminate between infected and healthy B. tabaci nymphs. The parasitoid treatment alone produced 36.3% mortality, with no mortality in the distilled water controls. The behavioural performance of the parasitoid could have either genetic or environmental causes. Bioassays studying the feeding habit of the imported mirid predator Macrolophus caliginosus (adults) and the indigenous mirid Camptotylus reuteri (nymphs and adults) on eggs, or early second instar nymphs of B. tabaci, and choice preference tests indicated a significant difference in feeding between M. caliginosus and C. reuteri. There was no significant difference in percentage feeding of M. caliginosus on eggs (2.2%) or second instar nymphs (8.0%). There was a significant difference in feeding of M. caliginosus adults (18.6%) when offered eggs and second instars in the same arena compared with eggs or second instars offered separately. These results could be attributed to the biological behaviour of the predator having a type III functional response. Studies with the local C. reuteri species showed no significant difference in adult and nymphal consumption on second instars of B. tabaci compared with nymphs on eggs. However, C. reuteri adults fed less on eggs compared with nymphs. This local predatory species appears to be more efficient than M. caliginosus in feeding on particular stages of B. tabaci without depending on prey density. This is further supported by the low consumption of both adults and nymphs in the choice test (4% and 2.3%, respectively) compared with M. caliginosus adults (18.6%).     

Biology of Tupiocoris cucurbitaceus (Hemiptera: Miridae), a predator of the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) in tomato crops in Argentina

The predator Tupiocoris cucurbitaceus is frequently found attacking Trialeurodes vaporariorum in greenhouses without pesticide applications in Argentina. The objective of these studies was to evaluate some biological characteristics of this species fed on three types of diet (whitefly nymphs, Sitotroga cerealella eggs and a mix of both) and on two host plants (tomato and tobacco), under controlled experimental conditions. Preimaginal developmental time for female and male bugs was shorter in the presence of whiteflies than with only moth eggs. Females lived longer when they ate only whitefly nymphs compared to a mixed diet or only moth eggs. The amount of adult descendants was greater when bugs could eat whiteflies, regardless of the presence of S. cerealella. Embryonic development time, male longevity and sex proportion were not affected by the diet or the host plant. Prey consumption was evaluated for three T. cucurbitaceus life history stages (fourth/fifth instar nymphs, female and male adults) on two types of prey (whitefly nymphs and S. cerealella eggs). On tomato, females were more voracious than males and nymphs. On tobacco, adults and nymphs consumed more S. cerealella than T.vaporariorum nymphs, but again, bug females preyed more than males and nymphs. Results demonstrate that T. cucurbitaceus can survive, develop and reproduce normally using both T. vaporariorum and S. cerealella eggs as prey on tobacco or tomato plants. This information can be useful for managing this predator against T. vaporariorum through conservative or augmentative biological control strategies.     

Immature stages of Pangaeus (Pangaeus) serripes (Westwood) (Hemiptera-Heteroptera: Cydnidae: Cydninae), associated with figs in Mexico

The immature stages of Pangaeus (Pangaeus) serripes are described for the first time. Immature stages are illustrated and notes about their biology are included. Morphological features of the legs of the nymphs are associated with the fossorial habit of the Cydninae. Both adults and nymphs have been reared and found feeding on fallen fruits and seeds of several species of figs in Mexico.     

Development of Encarsia bimaculata (Heraty and Polaszek) (Hymenoptera: Aphelinidae) in Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) nymphs

Encarsia bimaculata was recently described from India as a potentially useful parasitoid of Bemisia tabaci. Its developmental biology was studied in the laboratory at 25–30 °C and 70–75% RH. Results showed that E. bimaculata is a solitary, arrhenotokous, heteronomous, autoparasitoid. Mated females laid eggs internally in B. tabaci nymphs that developed as primary parasitoids. Males developed as hyperparasitoids, either in females of their own species or in other primary aphelinid parasitoids. Superparasitism was common under cage conditions. Both sexes have an egg, three larval instars, prepupal, and pupal stages. Development from egg to adult took 12.70 ± 2.10 days for females and 14.48 ± 2.60 days for males. Individual B. tabaci nymphs were examined for E. bimaculata parasitization using three isozymes: esterase, malate dehydrogenase, and xanthine dehydrogenase. All three isozymes showed differential banding patterns that identified E. bimaculata parasitized or unparasitized B. tabaci nymphs.     

Feeding habits of the predaceous nymphs of Dolania Americana in Northwestern Florida (Ephemeroptera : Behningiidae)

Feeding habits of nymphs of the predatory mayflyDolania americana Edmunds & Traver in northwestern Florida were examined during 1971 and 1972. Larvae of Chironomidae (Diptera) formed the bulk of prey items. The size of the predaceousD. americana nymphs was correlated with the size of chironomid prey taken. Differential microhabit utilization allows partition of prey resources with the other major predator species present. The relationship between predator and prey biomass throughout the year is discussed.     

Photoperiodic Control of Developmental Diapause in Nymphs of Prostriate Ixodid Ticks (Acari: Ixodidae)

Extrinsic control of developmental diapause in nymphs of prostriate ticks of the subgenus Ixodes sensu stricto (Ixodes ricinus and Ixodes persulcatus from Eurasia and Ixodes scapularis from North America) appears to be based on a complex two-step photoperiodic reaction of a short-day/long-day type. Diapause control in the subgenus Afrixodes (the South African tick Ixodes rubicundus) appears to be based on a simple long-day reaction. The option between non-diapause development and diapausing arrest in engorged nymphs is determined by both pre- and post-feeding photoperiodic regimes. Consequently diapausing arrest in engorged nymphs of Ixodes sensu stricto can be induced either by a short-day (after their engorgement) or by a long-day regime (in unfed nymphs), while active, non-diapause development is possible only when the short-day pre-feeding regime is followed by a long-day post-feeding regime. The photoperiodic response in I. (Afrixodes) rubicundus nymphs seems to be of the long-day type both before and after feeding. Consequently this non-diapause development is enabled by a long-day regime, while diapause is induced by a short-day regime of exposure. Nevertheless, there are some indications that the control of nymphal diapause in the latter species is also of a complex nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

PCR-based,rapid diagnosis of parasitism of Lygus spp. (Hemiptera: Miridae) by Peristenus relictus (Hymenoptera: Braconidae)

Several species of Lygus (Heteroptera: Miridae: Mirini) are serious crop pests in North America where their parasitism rate by native nymphal parasitoids is generally lower than in Europe. Peristenus relictus (Ruthe) (formerly P. stygicus Loan) (Hymenoptera: Braconidae: Euphorinae) is the predominant nymphal parasitoid of several Lygus spp. in the warm Mediterranean region and has been a candidate for introduction against Lygus hesperus Knight and L. lineolaris (Palisot de Beauvois) in the southern US. We report a rapid, sensitive, and specific PCR-based assay for diagnosis of P. relictus immature stages within Lygus nymphs that entails three steps: DNA extraction, PCR of the partial mitochondrial COI gene, and agarose gel electrophoresis. The PCR-based methodology is species-specific because the target DNA of other sympatric, congeneric species was not amplified with use of the primers developed for P. relictus diagnosis. The sensitivity of the PCR method, assessed through spike tests, was established by the detection of a ratio of 1:10,000 P. relictus DNA to Lygus DNA. Molecular diagnosis of parasitism of field collected nymphs is achievable in one day, eliminating the need to rear nymphs to obtain adult parasitoids for morphological identification.     

Ontogenetic Shift in Efficacy of Antipredator Mechanisms in a Top Aquatic Predator,Anax junius (Odonata: Aeshnidae)

The ability of prey to escape predation often lies in the occurrence and efficacy of their predator avoidance and antipredator behaviors, which are often coupled with specialized morphology. How the use and efficacy of these behaviors change throughout ontogeny may be indicative of the vulnerability and ecological roles these animals experience throughout their lives. We examined the antipredator behavior of a large dragonfly nymph, Anax junius, from a historically fishless pond where these animals have traditionally been classified as top predators. These dragonfly nymphs displayed a series of distinct aggressive antipredator behaviors when grasped that involved stabbing with lateral and posterior spines and seizing with labial hooks. Larger (older) nymphs displayed these aggressive behaviors significantly more than smaller (younger) animals in simulated predation trials. During encounters with live larval salamander predators (Ambystoma tigrinum), all large nymphs, but only 12.5% of small nymphs successfully escaped predation attempts by the amphibians through the use of antipredator behavior. Large nymphs were also significantly more active than smaller nymphs in the presence of salamander larvae. Despite often being considered top predators in fishless ponds, our study demonstrates that their true role is more complex, depending on ontogeny and body size, and that effective antipredator behavior is likely necessary for survival in these systems.     

Life history of the tick parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) in Kenya

We conducted laboratory and field experiments to elucidate the life history of Ixodiphagus hookeri, a parasitoid of the ixodid tick Amblyomma variegatum in Western Kenya. Ixodiphagus hookeri females oviposited in unfed host nymphs as well as engorged nymphs, but rarely in engorged larvae. While I. hookeri developed to adults in engorged nymphs, the eggs laid in unfed nymphs disappeared within 2 days after oviposition. As temperature increased, development time of I. hookeri from oviposition to adult emergence in engorged nymphs decreased from 46 days at 23 °C to 35 days at 28 °C, and their immature survival in engorged nymphs decreased from 67% at 23 °C to 22% at 28 °C. No parasitoid adult emerged from hosts at 30 °C. Individual hosts parasitized by single females produced 42–53 adult wasps, 73% of which were females. As a typical pro-ovigenic species, I. hookeri females had an average of 84 mature eggs at emergence and lived only for a few days. When laboratory-reared, unfed nymphs of A. variegatum were attached to cattle for 4–9 days in subsistence farmers’ fields in Western Kenya, 25% of the engorged nymphs and 4% of the unfed nymphs on cattle were parasitized by I. hookeri, demonstrating that I. hookeri females search for and oviposit in A. variegatum nymphs on cattle. Unlike other strains of I. hookeri that overwinter as eggs in unfed nymphs, I. hookeri could continuously reproduce throughout the year in Western Kenya.     

Entomopathogenic fungal infection (Deuteromycotina: Hyphomycetes) affects water relations of the german cockroach,Blattella germanica (L.) (Dictyoptera: Blattellidae)

• 1.1. The total body water, lipid content, and cuticular permeability of fungus infected and uninfected German cockroaches, Blattella germanica, were examined.
• 2.2. Infected adult cockroaches weighed less and had significantly more body water than did uninfected specimens of the same size.
• 3.3. Uninfected medium-size nymphs weighed significantly more than infected nymphs, but there was no difference in body size between infected and uninfected small nymphs.
• 4.4. Cuticular permeability and lipid content of infected and uninfected cockroaches was not significantly different.
• 5.5. Sequestering of water by the fungal cells is discussed as a possible factor in the pathology of this fungal parasite.